238 CHEMISTRY 



may be in preparation for warfare, for sanitary purposes, as aids in 

 the enforcement of revenue laws, or for their own protection as pur- 

 chasers of supplies; and so the usefulness of chemistry is felt along 

 innumerable lines. The science advances with ever-increasing rapidity 

 and there are as yet no signs of slackening. What shall the future be? 

 We can distinguish necessities and express our hopes, even if we can- 

 not prophesy. An essay of this kind would have small value if it 

 failed to offer any helpful suggestions for the work that is to be done. 



In the realm of descriptive chemistry certain work is obviously 

 needed and is therefore likely to be done. Part of this, and the least 

 attractive part, is revisionary a verification of the older data with 

 the correction of venerable errors. On the inorganic side we may 

 predict many advances, and some of the possible lines of research 

 we have already considered. In order to complete the periodic table 

 the rare earths must be exhaustively studied, and the irregularities 

 shown by iodine and tellurium, or by potassium and argon, ought to 

 be explained. The problems of chemical structure which are offered 

 by complex bases and acids and by double salts require elucidation, 

 and here physico-chemical methods are likely to be most applicable. 

 The correlation of chemical structure with crystalline form is sure to 

 receive much attention; but what direction researches of this kind 

 may take is not easy to foresee. 



For organic chemistry I am hardly qualified to speak, at least not 

 with regard to the more immediate urgencies. It is plain, however, 

 to every one that there are large and important groups of compounds 

 which await constitutional interpretation, the alkaloids and albumin- 

 oids being among thein. Organo-metallic bodies also deserve a good 

 deal of attention, for in them the two departments of descriptive 

 chemistry meet, and each one, organic or inorganic, can be made to 

 shed light upon the other. Finally, the relations between physical 

 properties and chemical composition are most easily investigated upon 

 the organic side, and here are problems enough to keep men busy for 

 a good part of the present century. All the properties of a substance 

 should be calculable from its composition; but the adequate data and 

 the conclusive theory are far beyond our reach. We have a few begin- 

 nings, nothing more. 



In physical chemistry, it seems to me, we find the unifying prin- 

 ciples which are to bind all the subdivisions of our science into one. 

 Some of the problems mentioned under the heading of descriptive 

 chemistry are almost wholly physical in their nature; only they are 

 statical, and leave dynamics untouched. They deal with equilibria 

 established by transformations of energy a statement which holds 

 true whether we connect it with the atomic theory or base it upon 

 the phase rule. The laws of chemical equilibrium are fundamental, 

 beyond question; but antecedent to their application there was an 



